I. Field
The following description relates generally to wireless communications, and more particularly to rate matching of messages containing system parameters in time division duplex (TDD) systems.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, . . . ). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Third Generation Partnership Project (3GPP) Long-Term Evolution (LTE) systems, Orthogonal Frequency Division Multiplexing (OFDM), and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple mobile devices. Each mobile device can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations. This communication link can be established via a single-input-single-output (SISO), multiple-input-single-output (MISO), single-input-multiple-output (SIMO), or a multiple-input-multiple-output (MIMO) system.
For instance, a MIMO system can employ multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas can be decomposed into NS independent channels, which are also referred to as spatial channels, where NS≦min{NT, NR} Each of the NS independent channels can correspond to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
A MIMO system can support a time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions can be on the same frequency region so that the reciprocity principle allows the estimation of the forward link channel from the reverse link channel. This can enable the access point to extract transmit beamforming gain on the forward link when multiple antennas are available at the access point
Wireless communication systems oftentimes employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to a mobile device. A mobile device within the coverage area of such base station can be employed to receive one, more than one, or all the data streams carried by the composite stream. Likewise, a mobile device can transmit data to the base station or another mobile device.
Typically, when communication is being established between a mobile device and a base station, the mobile device has limited information regarding the base station. During initial communication between the mobile device and base station, the base station can transmit certain messages, such as system parameter messages, via primary broadcast channel (PBCH) and physical downlink shared channel (PDSCH), which can comprise dynamic broadcast channel (DBCH), to the mobile device, where the PBCH and DBCH each can contain respective portions of the system parameters associated with the wireless system, in general, and with the base station, in particular, to facilitate communication with the mobile device.
To facilitate communication, the communication system can employ radio frames that can comprise subframes, which can be designated for downlink or uplink transmission of data between the base station and mobile device. Typically, a subframe can comprise two slots. A specified number of symbols (e.g., encoded data, such as system parameter information) can be contained in the slots of a subframe. However, during downlink transmission of DBCH, in a frame sequence where an uplink subframe immediately follows a subframe containing the DBCH, a portion of the resource elements (e.g., associated with a corresponding symbol and sub-carrier) at the end of the second slot is typically allocated as guard time, which is related to downlink to uplink switching time, to enable the mobile device time advance its uplink transmission. As a result, data (e.g., symbols) associated with the PDSCH, including DBCH, that appears in this guard time region can be omitted, erased, or otherwise eliminated. This results in inefficiency for the mobile device attempting to acquire the base station, as one parameter the mobile device typically will not know in advance is the guard time employed by the base station, and the guard time can vary. Further, allocation of an uplink subframe may not always immediately follow a subframe containing the DBCH.
It is desirable to reduce or eliminate inefficiency related to data, which can be DBCH and/or other information associated with the PDSCH, in the guard time region being omitted, erased, or otherwise eliminated, so that the mobile device can more efficiently acquire and establish communication with the base station. By reducing or eliminating omission, erasure, or elimination of data, such as DBCH, the mobile device can more efficiently receive the system parameters associated with the base station and can be configured more efficiently to optimize communication between the mobile device and base station.